[The study on Pseudomonas aeruginosa infection in a hospital--2. Bacteriological study]

We investigated the hospital acquired infection of P. aeruginosa in urological wards by determining the serotype and testing the sensitivity of this bacteria to antibiotics. The results were as follows: 1. 92 strains of G-serotype (22.2%), 76 of A-serotype (18.3%) and 65 of B-serotype (15.7%) were predominantly found in the serotype distribution of 415 P. aeruginosa strains isolated from urine or feces. 2. Comparing the sensitivity of P. aeruginosa to various antibiotics determined by MIC50 (the concentration to inhibit growth of 50% of the objective bacteria), Dibekacin showed MIC50 of 0.78 microgram/ml, Ceftazidime 1.56 micrograms/ml, Cefsulodin 3.13 micrograms/ml, and Polymixin-B, Piperacillin, Aztreonam 6.25 micrograms/ml. The analysis of the relationship between serotype and sensitivity to antibiotics demonstrated that K-serotype of P. aeruginosa tended to be highly sensitive and M-serotype be less sensitive to only Dibekacin. There was no definite relation of serotype to sensitivity against any other antibiotics. The comparison of sensitivity to antibiotics determined by MIC50,80 between P. aeruginosa isolated from urine and that from feces revealed that the former was less sensitive by one to four grades than the latter. The sensitivity of P. aeruginosa isolated from feces at admission was not different from that at discharge. In the chronological changes in sensitivity of P. aeruginosa isolated from urine, the strains highly resistant to Cefsulodin, Ceftazidime, Aztreonam and Dibekacin had increased in 1984 and 1985. 3. These highly resistant strains tended to break out in the urological wards, which suggested the need for more intensive prophylactic measures against hospital acquired infection.